1. Field of the Invention
The present invention pertains to iron clubs for use on fairways, and on tees from time to time, generally to approach the greens on a golf course. The object is to retard the tendency of the right-handed golfer to hit the ball with left to right spin in the case of longer irons, i.e., Nos. 1, 2, 3, 4, or pull the ball to the left of target when using the shorter, more lofted irons, i.e., Nos. 7, 8, 9 and 10 (vice versa if the player is left-handed).
2. Description of the Prior Art
Today, designs of clubs are essentially regulated by the United States Golf Association, among others, who have design constraints so that the element of skill is not removed from the playing of the game. Notwithstanding such constraints, golfers in general seek game improvement aids. Many have been made over the last decade consistent with the rules of the governing bodies.
Over the course of time, it has been noted and well recorded that golfers have difficulties with long irons, particularly Nos. 1, 2 and 3. Many golfers have been known to purchase such clubs but never use them in play due to difficulty of use. One particular difficulty is commonly called "slicing". The golfer imparts a spin on the ball such that it travels through the air with a pronounced curve away from his target line, to the side of the course he was facing while at address, prior to swinging at the ball. While expert golfers can deliberately make such shots to suit particular game conditions, such "slicing" is generally considered poor, yielding loss of distance and control. While no design can purport to completely eliminate "slicing" and yet conform to the constraints of the governing bodies, repeated experiments have shown the tendency can be retarded.
A second difficulty occurs with shorter clubs, i.e., Nos. 7, 8, 9 and 10, commonly called "pulling". The ball tends to travel off the target line, to the side of the course opposite to where the golfer was facing at address. Often this is a result of the same swing plane used on the longer irons to produce "slicing", but due to the fact that the clubs are shorter, with consequent less drag during the swing, the resultant shot often results in an undesirable "pull".
To understand the force the golfer must exert to attain a desired club head speed, one should view the swing as a rotating body. See U.S. Pat. No. 4,058,312 to Stuff, et al., where FIG. 1 illustrates the circular pattern of the swing. Since the head of the club is the predominant weight, the swing produces the well-known fly wheel effect. The net torque the golfer must supply to produce the desired swing speed is equal to moment of inertia times angular acceleration (T=ML.sup.2 .times.A). Since moment of inertia must be calculated by taking all the several weights contained in a club and multiplying by the length squared of each weight measured back to the end of the grip, it is apparent that any weight location in the head has a large bearing on the amount of force the golfer must supply, since this is the maximum distance zone from the grip or axis of rotation.
If one were to view the plane of the golf swing from a vantage point above the golfer, looking down on the player, a circular motion will also be observed. Clearly, the head of the golf club, at furthest length from the axis of rotation, is the part of the club travelling at highest velocity. In the well-known Impulse-Momentum laws governing bodies in collision, it can be seen that the momentum (MV) will be increased should the weight of the head be placed more towards its toe. (See U.S. Pat. No. 3,059,926 to Johnstone).
In ideal circumstances, whenever momentum can be increased, the distance the golf ball will travel must also be increased. Were this the sole factor in producing acceptable to good golf shots, all clubs might well be toe weighted to maximize momentum. It has been observed that the vast preponderance of golfers swing their clubs at either their personal comfort zone (near maximum power) up to maximum power. A very slight increase in effective length of mass to axis of rotation will frequently cause acceleration to be reduced (acceleration equals force divided by moment of inertia) thus reducing club head velocity at impact. Observations show that such as action tends to twist the club head open and accounts for the persistence of long iron slicing.
Since the length of the shorter clubs, such as a 9-iron, is ordinarily 351/2 inches, and is 31/2 inches less than a 2-iron of such a set, the length difference being squared in torque calculations, the golfer has an easier time accelerating a short club in spite of the heavier head found in such a club. This accounts for the persistence of short club pulling.
Table I, below, illustrates how typical iron shaft lengths, for both men and women, decrease as the loft of each club increases.
TABLE I ______________________________________ TYPICAL IRON SHAFT LENGTHS IRON NUMBER MEN LADIES ______________________________________ 1 391/2 INCHES 381/2 INCHES 2 39 INCHES 38 INCHES 3 381/2 INCHES 371/2 INCHES 4 38 INCHES 37 INCHES 5 371/2 INCHES 361/2 INCHES 6 37 INCHES 36 INCHES 7 361/2 INCHES 351/2 INCHES 8 36 INCHES 35 INCHES 9 351/2 INCHES 341/2 INCHES 10 351/2 INCHES 341/2 INCHES 11 35 INCHES 34 INCHES ______________________________________
Prior art has generally designed iron golf club heads in one of two ways:
To understand the force the golfer must exert to attain a desired club head speed, one should view the swing as a rotation body. See U.S. Pat. No. 4,058,312 to Stuff, et al., where FIG. 1 illustrates the circular pattern of the swing. Since the head of the club is the predominant weight, the swing produces the well-known fly wheel effect. The net torque the golfer must supply to produce the desired swing speed is equal to moment of inertia times angular acceleration (T=ML.sup.2 .times.A). Since moment of inertia must be calculated by taking all the several weights contained in a club and multiplying by the length squared of each weight measured back to the end of the grip, it is apparent that any weight location in the head has a large bearing on the amount of force the golfer must supply, since this is the maximum distance zone from the grip or axis of rotation.
If one were to view the plane of the golf swing from a vantage point above the golfer, looking down on the player, a circular motion will also be observed. Clearly, the head of the golf club, at furthest length from the axis of rotation, is the part of the club travelling at highest velocity. In the well-known Impulse-Momentum laws governing bodies in collision, it can be seen that the momentum (MV) will be increased should the weight of the head be placed more towards its toe. (See U.S. Pat. No. 3,059,926 to Johnstone).
In ideal circumstances, whenever momentum can be increased, the distance the golf ball will travel must also be increased. Were this the sole factor in producing acceptable to good golf shots, all clubs might well be toe weighted to maximize momentum. It has been observed that the vast preponderance of golfers swing their clubs at either their personal comfort zone (near maximum power) up to maximum power. A very slight increase in effective length of mass to axis of rotation will frequently cause acceleration to be reduced (acceleration equals force divided by moment of inertia) thus reducing club head velocity at impact. Observations show that such as action tends to twist the club head open and accounts for the persistence of long iron slicing.
Since the length of the shorter clubs, such as a nine iron, is ordinarily 351/2 inches, and is 31/2 inches less than a two iron of such a set, the length difference being squared in torque calculations, the golfer has an easier time accelerating a short club in spite of the heavier head found in such a club. This accounts for the persistence of short club pulling.
A. The center of mass of the head was in the center of the face of the head, viewed in the vertical plane (FIG. 1); or
B. The center of mass was in the toe area of the long clubs, progressing gradually towards the heel area of the short clubs, commonly called "flow weighting" (FIGS. 2 and 3).
The design contained herein addresses the problems of slicing and pulling using differentiated club heads for each iron in a normal set of clubs.